1. Field of the Invention
This invention relates to magnetizable overlay structures for controlling the movement of magnetic single wall domains using field access propagation techniques and, more particularly, to chevron-shaped, field access drive structures.
2. Description of the Prior Art
At present, devices that utilize magnetic single wall domains typically use soft magnetic overlay structures for propagation and storage. Examples include the T-bar, T-X and X-bar structures. Currently, the chevron structure is most frequently used only for detection, although it may also be used for storage and has certain advantages in this regard, as discussed below.
Propagation structures that are of a chevron pattern may incorporate redundancy. That is, the individual chevron-shaped elements are formed into columns trasverse to the direction of domain propagation. These chevron columns stretch or expand single wall domains into strip-like form. Because of this redundancy of elements, chevron structures are less sensitive to pattern defects than are structures formed from other patterns (which form single wall domains which more closely approximate a circular cross section and are frequently termed "bubble" domains).
Chevrons are also relatively insensitive to gaps between the chevrons. In addition, strip domains formed by chevrons are less sensitive than are bubble domains to fluctuations in magnetic conditions resulting from defects or other inhomogenities in the garnet materials that frequently are used in magnetic domain devices. Finally, chevrons have relatively high drive fields and therefore are more amenable to high frequency operation than other patterns.
As a result of at least these advantages, chevron structures have excellent potential for use as propagation structures in storage loops. In addition, the chevron structure will undoubtedly continue to be used for such functions as strip detection.
IEEE Trans. Mag., Vol. Mag. 9, No. 3, Sept. 1973, pp. 433-66, entitled "Magnetic Bubble Memory Chip Design", relates to structures for transferring domains between chevron and T-bar propagation structures. However, in order to fully implement chevron structures both to propagate domains and also in connection with strip detection, it is desirable to provide structures that are capable of smoothly and effectively transferring domains from chevron structures to other types of structures, such as T-X and X-bar structures, and vice versa.